Exploring the Relationship Between Volumes, Crashes, and Speeds
Exploring the Relationship Between Volumes, Crashes, and Speeds
Using BikePed Portal data, this case study examines the relationships between bike and pedestrian volumes, surrounding vehicle speeds (RITIS), and bike/ped crashes occurred around permanent count locations. In crash analysis, the exposure effect to motorized vehicles is one of the most important crash risk factors. A typical way to measure the exposure effect is to count the volume of each mode. In addition, vehicle speed has a significant impact on the severity of the crash. Therefore, this case study studies whether the frequency of crashes is affected by volumes of pedestrians and cyclists and vehicle speed. The study sites are permanent count locations in the state of Oregon, Washington, D.C., and Arlington County, Virginia. The study uses the most recent data available (2018-2023).
The spatial unit is the space within a half-mile straight-line buffer from the permanent count location. This was set because it is difficult to measure the traffic volume by mode at all points where a collision between modes can occur. Given that traffic volume affects the frequency of crashes, it was assumed that the number of bicycles or pedestrians measured within a half-mile would represent the traffic volume accounting for those crashes.
Location: Oregon, Virginia, Washington D.C.
Analysis Year: 2018-2023
Used Data: bike & pedestrian count (volume), crash , Census Block group, speed
Data Source/Year
| Data | Source | Year |
|---|---|---|
| Bike/Pedestrian Counts | BikePed Portal | 2018–2023 |
| Bike/Pedestrian–involved Crash | ODOT*, VDOT, DDOT | 2018–2023 |
| Land Use (Zoning) Type–DC | Open Data DC | 2016 |
| Land Use (Zoning) Type–OR | Oregon GEOHub Data | 2023 |
| Land Use (Zoning) Type–VA | Arlington Virginia ACMaps | 2021 |
| Census Block Group Population & Land Area–DC | Open Data DC | 2020 |
| Census Block Group Population & Land Area–OR | Oregon GEOHub Data | 2020 |
| Census Block Group Population & Land Area–VA | Virginia Open Data Portal | 2020 |
| Speed–DC, OR, VA | RITIS | 2018–2023 |
*Note that ODOT provides crash data with location information through 2022. Since location information is a very important feature in this study, only cases where the location of each crash case was provided were analyzed.
Population Density is the average value within half-mile straight buffer area from the Bike/Ped Volume Counting Spot using census block group population number and area (square-mile)
Following characteristics of pedestrian and bike volume and crash counts are accumulated of each permanent count location
No count numbers for the “Bridge” and “Intersection” doesn’t mean that there are no cyclists on the bridges or intersections. It means that the number of cyclists was not collected on the bridges and intersections.
No count numbers for the “Bikelane”, Bridge” and “Intersection” doesn’t mean that there are no pedestrians on the bike lanes, bridges or intersections. It means that the number of pedestrians was not collected on the bike lanes, bridges and intersections.